Of all the buildings that architectural preservationists try to save, industrial buildings are the hardest sell. They are big, expensive to preserve, heat and maintain, and they are not cute. It's really hard to find good uses for them. In Essen, Germany, there are not too many of them; most of the area was bombed flat in World War II. Somehow the Zollverein Coal Mine complex survived the war intact, only to fall into disuse in the eighties as Germany moved to cleaner fuels and dirty steelmaking was offshored.

More surprisingly, the whole complex was preserved and became a world heritage site.